Conventional lamp devices may use a GX53-type cap, for example. This lamp device is generally flat in shape. The GX53-type cap is provided on the upper surface side of the lamp device, and a metallic cover is arranged on the lower surface side thereof. A flat fluorescent lamp is arranged in the metallic cover as a light source. The metallic cover is separate from, but in contact with, the cap. A lighting circuit for lighting the fluorescent lamp is housed inside the cap. Heat generated by lighting of the fluorescent lamp is radiated outside from the metallic cover, thereby suppressing thermal influences on the lighting circuit, etc. (refer to, for example, PTL 1).